These are the Valid field entries for straight-line depreciation: Full-year, Half-year, Zero in first year, Full-month, Mid-month, and Zero in first month.

Full Month: An asset has an equal depreciation amount every month, starting with the first month in service and continuing throughout its useful life.

Mid Month:  Mid-month charges a full month's worth of depreciation in the asset's first month of life if the Date in service is before the 16th. If the Date in service is after the 15th, then $0 is charged in the first month of life and an 'extra' month is added to the asset's useful life to charge the amount not charged in the first month of life.

Zero Month:  The asset will not depreciate in its first month in service.  Starting with the second, it will depreciate equally over its useful life in the same manner as Full Month.

Full Year:  Full Year will calculate an entire year's depreciation for the first year, REGARDLESS of the month it was placed in service.  During the first year, the annual depreciation will be distributed over the number of months(periods)it is in service for the first year.  Example: If the asset is placed in service in the third period, then the first year's depreciation will be evenly distributed between periods three and twelve.  After the first year, the asset will depreciate in the same manner as Full Month.

Half Year:  One half of a normal year's depreciation will be depreciated in the first year.  The actual amount of depreciation will be distributed over the number of periods the asset is in service during the first year.  Beginning with the second year, a full years' depreciation is taken, until the last year when an additional half year's depreciation is taken.

Zero Year:  With this convention, the asset accumulates no depreciation in the first year. In the first period of the asset's second year, it will start depreciating in the same manner as Full Month.